Printed circuit boards (PCBs) are generally mounted in frames, with a large number of PCBs mounted in each frame, with as high a density as possible, in order to save space. A typical PCB comprises a pattern of electrical interconnections on a flat rectangular sheet of insulating material carrying a number of components. The four edges of the PCB can be referred to as a front edge, a back (or rear) edge, a top edge, and a bottom edge. The PCB slides into guide channels in the frame, the PCBs lying normally in a vertical plane with the top edge in a top guide channel, the bottom edge in a bottom guide channel, and the rear edge carrying a set of connections which mate with a corresponding set of connections mounted to the frame. The front edge of the PCB may carry two devices (one usually near the top, and one usually near the bottom) to aid in inserting, removing or retaining the PCB relative to the frame.
Various prior art devices for performing this function are depicted in the following U.S. patents and attention is directed to them: U.S. Pat. No. 4,648,009 dated Mar. 3, 1987 to R. A. Beun et al.; U.S. Pat. No. 4,632,588 dated Dec. 30, 1986 to M. H. Fitzpatrick; U.S. Pat. No. 4,606,591 dated Aug. 19, 1986 to K. A. Bloch; U.S. Pat. No. 4,596,907 dated June 24, 1986 to A. S. LaGreco et al.; U.S. Pat. No. 4,445,740 dated May 1, 1984 to K. L. Wallace; U.S. Pat. No. 4,313,150 dated Jan. 26, 1982 to Pak-Jong Chu; U.S. Pat. No. 4,233,646 dated Nov. 11, 1980 to E. C. Leung et al.; U.S. Pat. No. 4,064,551 dated Dec. 20, 1977 to R. Lightfoot; U.S. Pat. No. 3,952,232 dated Apr. 20, 1976 to R. A. Coules; and U.S. Pat. No. 3,798,507 dated Mar. 19, 1974 to N. F. Damon et al. Another prior art device is pictured on pages 78 and 79 of the Fall 1975 issue of Telesis published by Bell-Northern Research Ltd., Ottawa, Ontario, Canada.
The Leung patent discloses a latching lever having a latching mechanism which comprises a hooked portion flexibly connected to the body portion of the latching lever, an actuating member solidly connected to the hooked portion for moving the hooked portion relative to the body portion, and a stop portion, solidly connected to the body portion for limiting the movement of the actuating member. A stud carried by the PCB is engaged by the hooked portion of the lever to enable the lever to latch. Moving the actuating member disengages the hooked portion from the stud, thereby unlatching the lever, and leaving the lever free to pivot about its pivot point.
Prior art devices of the type described above have the disadvantage of having weak areas, such as where the actuating member and the hooked portion are attached, which may not withstand the stresses incurred from repetitive insertion and removal of a PCB. Over time the web joining the actuating member, or the hooked portion, to the lever may wear out allowing either, or both, to break off. Without these items the device will not function as intended.
Other prior art devices, such as described in the Chu patent, have the disadvantage that the lever must be attached by means of a rivet or screw and nut assembly. This can add to the cost and time of manufacturing and assembling the lever.